Abstract
The aim of this study was to examine glycoconjugate secretion in human airways with and without an epithelium. Glycoconjugate release in supernatants derived from human airways in vitro was determined using an ELISA assay with an anti-human mucin monoclonal antibody (MAb 3D3). This monoclonal antibody reacted strongly with Le(b) antigen but also recognized in vitro Le(a) and Le(y) determinants. In 11 of the 34 different lung samples (32%) studied the glycoconjugate levels were below the threshhold of detection for this assay. The mean basal secretion of glycoconjugates in human airways in vitro was 100+/-28 microg/g tissue (Period I; n = 23 different lung samples). The amount of glycoconjugate measured in the medium derived from human isolated bronchial ring preparations did not change under control conditions during the course of the experimental procedure (Period I; 128+/-46 microg/g tissue and Period II; 159 +/-48 microg/g tissue; n = 13 paired lung samples). In the supernatants of airway preparations with an intact epithelium the amount of glycoconjugates detected was 90+/-38 microg/g tissue (Period I; n = 12 different lung samples) and removal of the epithelium did not alter this basal glycoconjugate release (94+/-60 microg/g tissue: Period I, n = 8 different lung samples). The absence of the epithelial layer was confirmed by histological evaluation. Methacholine (100 microM) induced a 10- and four-fold increase in glycoconjugate release from airways with and without an epithelium, respectively. In contrast, in preparations with an epithelium, LTD4 (10 microM) and anti-IgE (dilution: 1/1000) did not cause an increase of glycoconjugate release. The methacholine difference between airways with and without an epithelium was not significantly different (P > 0.10). However, a treatment with atropine (100 microM) prevented the increase of glycoconjugate release in preparations with an epithelium. These data derived from a limited number of experiments suggest that the epithelium may not regulate the basal or stimulated release of glycoconjugates from isolated human airways.
Highlights
Studies[1,2] showed that the constituents of mucus are derived from goblet cells and the submucosal glands
Coles and coworkers[3] using 14C-glucosamine, measured radiolabelled glycoprotein in the tissue medium from airway preparations and demonstrated that the epithelium did not contribute to the basal secretion in dog respiratory tract
In human bronchial ring preparations after treatment with MAb 3D3, staining showed that this MAb 3D3 antibody was associated with tw o specific tissue regions, namely, the epithelial layer and submucosal glands (Fig. 2)
Summary
Studies[1,2] showed that the constituents of mucus are derived from goblet cells and the submucosal glands. While the principal constituents of mucus are the mucins, a variety of proteins, glycoconjugates (serum type glycoproteins and proteoglycans) and glycolipids are produced and secreted.[6,7,8] In an attempt to characterize those factors w hich constitute respiratory secretion, Saint George and coworkers[9] showed that a number of monoclonal antibodies reacted w ith material in goblet cells and/or submucosal mucus gland cells, data which have been confirmed by other investigators.[10] Recently, Emery and coworkers[11] have prepared an anti-human mucin MAb against purified human respiratory mucins These authors indicated that this anti-human MAb 3D3 was not specific for respiratory mucin but reacted, strongly with the Lewis b (Leb) antigen, and recognized Lea and Ley determinents using synthetic oligosaccharides. These observations suggested that this monoclonal may be a useful tool to monitor secretory activity in human airways
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